Optical response of electrons in a random potential

Using our recently developed Chebyshev expansion technique for finite-temperature dynamical correlation functions we numerically study the AC conductivity $\sigma(\omega)$ of the Anderson model on large cubic clusters of up to $100^3$ sites. Extending previous results we focus on the role of the boundary conditions and check the consistency of the DC limit, $\omega\to 0$, by comparing with direct conductance calculations based on a Greens function approach in a Landauer B\"uttiker type setup.